"On the customs declaration, the smugglers identified it as granite for construction and decoration of office space," Larisa Ledovskikh, a spokeswoman for customs at Moscow's Domodedovo airport, told AFP on Thursday.

"But our officials could see it was clearly not granite!"

The two smugglers -- who also tried to ship out silver antiques, fossils, semi-precious stones, microscopes and old books in the suspect cargo -- were initially charged with making a false declaration on their customs form.

Only after a three-month investigation did officials discover that the mystery lumps were fragments from outer space and the men part of a larger crime ring including experts and scientists, Ledovskikh said.

"They were part of an organized criminal gang. They had worked out a plan in advance to smuggle out of Russian territory and to the Czech Republic... two meteorite chunks, each weighing 100 grams," she said.

The two men were arrested on Sunday and charged with contraband, a sentence that carries a maximum of 12 years in prison in Russia.